Porting libsndfile, I see that the Debian developers use /dev/full, which apparently is what I think it is (Debian manpage below). Would it be useful to have something like that in OpenBSD, to test out-of-space behaviour of software?
Jan NAME full - always full device CONFIGURATION If your system does not have /dev/full created already, it can be created with the following commands: mknod -m 666 /dev/full c 1 7 chown root:root /dev/full DESCRIPTION File /dev/full has major device number 1 and minor device number 7. Writes to the /dev/full device will fail with an ENOSPC error. This can be used to test how a program handles disk-full errors. Reads from the /dev/full device will return \0 characters. Seeks on /dev/full will always succeed. FILES /dev/full SEE ALSO mknod(1), null(4), zero(4)